Minimally-invasive or percutaneous techniques for implanting bioprosthetic implants are commonly used in vascular and cardiovascular procedures. Such techniques involve the use of a delivery device, such as a catheter, to access a desired location via the patient's vasculature rather than using an open surgical approach where internal organs or tissue are exposed. The benefit of percutaneous procedures is in the ease of introducing devices into the patient without large cut downs, which can lead to long recovery times for patients.
One limitation of percutaneous procedures is the delivery profile of the bioprosthetic implant and delivery device. Because access to the desired implantation site is gained via the patient's vasculature, the delivery profile of the bioprosthetic implant and the delivery device, combined, must be sufficiently small so as to permit passage.
One method of reducing the delivery profile is to crimp the bioprosthetic implant about the delivery device. Crimping, however, may not reduce the delivery profile to a desired size due to the inherent bulk or configuration of the bioprosthetic implant. Therefore, changes are often required to the material and/or construction of the implantable bioprosthesis to permit crimping to yet smaller delivery profiles.
Replacement heart valves, for example, comprise a leaflet structure and a support structure. The leaflet structure is typically made from biological tissue, such as bovine pericardium, and the thickness of the tissue that makes up the leaflet structure limits the extent to which the heart valve can be crimped. Additionally, biological tissue will typically exhibit variations in thicknesses and these variations often produce unpredictable results with respect to the delivery profile of the crimped valves.
While the use of artificial or polymeric materials can offer a greater degree of control and flexibility to the resulting thickness of the material used for bioprosthetic implants, such materials may not always be desirable from at least a hemodynamic standpoint and may require the patient to take anticoagulants to prevent adverse effects from the interaction of the artificial material and the blood.
Another option is to remove excess portions of biological tissue so as to provide a thinner tissue having a consistent thickness throughout. The loss of tissue, however, can undesirably compromise the fiber structure and therefore the strength of the tissue. Compression of the tissue to produce a thinner tissue may be desirable. The compressed tissue, however, may spring back to its original and uneven thickness after compressive forces are released.
Therefore, what is needed are methods and devices for preparing a biological tissue adapted for a bioprosthetic implant and which reliably reduces the delivery profile for use in minimally-invasive and percutaneous procedures.